Transport protein which is used to introduce chemical compounds into nerve cells

ABSTRACT

The invention relates to a transport protein which can be obtained by modifying the heavy chain of the neurotoxin formed by  Clostridium botulinum.  The protein binds specifically to nerve cells with a higher affinity as the native neurotoxin. The invention also relates to a method for the production of transport protein, the nucleic acids coding for the transport protein, the transport protein containing pharmaceutical and cosmetic compositions and use thereof.

The present invention relates to a transport protein which binds to neurons, is accommodated by receptor-mediated endocytosis and is translocated from the acid, endosomal compartment into the cytosol of neurons. This protein is used as a transporting means for translocating other chemical substances (e.g. proteases), which are unable physiologically to penetrate into the cytosol of nerve cells through the plasma membrane. The present invention relates to the use of a transport protein for inhibiting the release of neurotransmitters.

Nerve cells release transmitter substances by exocytosis. The fusion of the membranes of intracellular vesicles with the plasma membrane is referred to as exocytosis. In the course of this process the vesicular contents is simultaneously discharged into the synaptic gap. The fusion of the two membranes is regulated by calcium, reacting with the protein synaptotagmin. Together with other co-factors synaptotagmin controls the status of three so-called fusion proteins, SNAP-25, synaptobrevin 2 and syntaxin 1A. While syntaxin 1A and synaptobrevin 2 are integrated into the plasma and/or vesicle membrane, SNAP-25 binds only lightly to the plasma membrane. To the extent that the intracellular calcium concentration increases, the three proteins bind to one another, both membranes approaching one another and subsequently fusing together. In the case of cholinergic neurons acetyl choline is released, causing muscle contractions, perspiration and other cholinergically provoked reactions.

The above mentioned fusion proteins are the target molecules (substrates) of the light chains of the clostridial neurotoxins, formed by the bacterium Clostridium botulinum.

The anaerobic, gram-positive bacterium Clostridium botulinum produces seven different types of protein neurotoxins. The latter are referred to as the Botulinus neurotoxins (BoNT/A to BoNT/G). Among these, in particular BoNT/A and BoNT/B cause a neuroparalytic disorder in humans and animals, referred to as botulism. The spores of Clostridium botulinum can be found in the soil, but may also develop in incorrectly sterilised and sealed home-made food preserves, to which many cases of botulism are attributed.

BoNT/A is the most lethal of all known biological substances. As little as 5-6 pg of purified BoNT/A represents an MLD (Multiple Low Dose). One unit (Engl.: Unit, U) of BoNT is defined as the MLD, killing half of the female Swiss Webster mice, each weighing 18-20 g, after intraperitoneal injection. Seven immunologically different BoNTs were characterised. They are denoted as BoNT/A, B, C₁, D, E, F and G and may be distinguished by neutralisation with serotype-specific antibodies. The different serotypes of BoNTs differ in affected animal species with regard to severity and duration of the paralysis caused. Thus, with regard to paralysis, BoNT/A is 500 times more potent in rats for example, than BoNT/B. In addition, BoNT/B has proved to be non-toxic in primates at a dosage of 480 U/kg of body weight. The same quantity of BoNT/A corresponds to 12 times the lethal dose (LD) of this substance in primates. On the other hand, the duration of paralysis after BoNT/A injection in mice is ten times longer than after injection of BoNT/E.

BoNTs have been used clinically for treating neuromuscular disorders, characterised by hyperactivity in skeleton muscles, caused by pathologically overactive peripheral nerves. BoNT/A has been approved by the U.S. Food and Drug Administration for treating blepharo-spasm, strabism and hemi-facial spasms. Compared with BoNT/A the remaining BoNT serotypes are evidently less efficacious and manifest a shorter duration of efficacy. Clinical effects of BoNT/A administered peripheral-intramuscularly are usually noticeable within a week. The duration of symptom suppression by one single intramuscular injection of BoNT/A is normally about 3 months.

The clostridial neurotoxins specifically hydrolyse different proteins of the fusion apparatus. BoNT/A, C₁ and E split SNAP-25, while BoNT/B, D, F, G as well as tetanus neurotoxin (TeNT) attack the vesicle-associated membrane protein (VAMP) 2—also referred to as synaptobrevin 2—. BoNT/C₁ furthermore splits syntaxin 1A.

The Clostridium bacteria release the neurotoxins as single-chain polypeptides each having 1251 to 1315 amino acids. Thereafter endogenous proteases split each of these proteins at a defined location into 2 chains each (‘nicking’), the two chains however remaining interlinked by a disulphide-bridge. These dual-chain proteins are referred to as holo-toxins (see Shone et al. (1985), Eur J Biochem 151, 75-82). The two chains have different functions. While the smaller fragment, the light chain (light chain=LC), represents a Zn²⁺-dependent endoprotease, the larger unit (heavy chain=HC) represents the transporting means of the light chain. By treating the HC with endopeptidases two 50 kDa fragments were brought about (see Gimenez et al. (1993), J Protein Chem 12, 351-363). The amino-terminal half (H_(N)-fragment) integrates into membranes at a low pH-value and enables the LC to penetrate into the cytosol of the nerve cell. The carboxy-terminal half (H_(c)-fragment) binds to complex polysialogangliosides, occurring exclusively in nerve cell membranes and to protein receptors not identified to date (Halpern et al. (1993), Curr Top Microbial Immunol 195, 221-241). The latter explains the high neuroselectivity of the clostridial neurotoxins. Crystalline structures confirm that BoNT/A disposes of three domains, which may be harmonised by the three steps of the action mechanism (see Lacy et al. (1998), Nat Struct Biol 5, 898-902). Moreover, these data give rise to the conclusion that within the H_(C)-fragment two autonomous subunits (sub-domains) exist of 25 kDa each. The first proof for the existence of the two functional sub-domains was brought about by the amino-terminal (H_(CN) and the carboxy-terminal half (H_(CC)) of the H_(C)-fragment of the TeNT, which were expressed in recombinant form and which revealed that the H_(CC)—, but not the H_(CN) domain binds to neurons (see Herreros et al. (2000), Biochem J 347, 199-204). The protein receptor-binding site of the synaptotagmin was discovered inside the H_(CC)-domains of BoNT/B and G, proving their separate functionality (see Rummel et al. (2004), J Biol Chem 279, 30865-70).

Under physiological conditions the HC binds to neuronal gangliosides, is received inside the cell by receptor-mediated endocytosis and reaches the natural vesicle circulation via the endosomal compartment. In the acid medium of the early endosomes, H_(N), the amino-terminal half of HC, penetrates into the vesicle membrane and forms a pore. Each substance (X), linked to HC via a disulphide bridge, will be split off the HC by intracellular redox systems, gaining access to the disulphide bridge and reducing it. X will ultimately appear in the cytosol.

In the case of the clostridial neurotoxins the HC is the carrier of an LC, splitting its specific substrate in the cytosol in the final step. The cycle of complex formation and dissociation of the fusion proteins is interrupted and the release of acetyl choline is consequently inhibited. As a result thereof, striated muscles are paralysed and sweat glands cease their secretion. The active period of the individual BoNT serotypes differs and depends on the presence of intact LC in the cytosol. As all neurons possess receptors for clostridial neurotoxins, it is not only the release of acetyl choline which may be affected, but potentially also the release of the substance P, of noradrenalin, GABA, glycine, endorphin and other transmitters and hormones.

That the cholinergic transmission is blocked preferentially, may be explained by the fact that the HC in the periphery enters into the neuron. Central synapses are protected by the blood-brain-barrier, which cannot be surmounted by proteins.

The HCs possess a high affinity for peripheral nerve cells, mediated predominantly by the interaction with complex polysialogangliosides—these are glycol lipids composed of more than one sialine acid (see Halpern et al. (1995), Curr Top Microbiol Immunol 195, 221-41). As a result, the LCs binding to them reach only this cell type and become active only in these cells. BoNT/A and B bind merely one molecule ganglioside GT1b each.

In order to research the role played by the amino acids, which build the binding pocket, a recombinant H_(C)-fragment was produced according to the invention. This technique permits to exchange individual amino acids. Thus, positively-charged amino acids may be substituted by negatively-charged or neutral amino acids, and vice versa. Slight modifications in the surface of the binding pocket produce no dramatic effect regarding the passing ability of the gangliosides. It could be shown that the affinity receded by more than 99%, if e.g. the amino acid in position 1266, the tryptophane—referred to as W in the SXWY-motive—is substituted by an aliphatic residue, e.g. leucine. However, the contrary has also been observed. The substitution of amino acids, extending into the binding pocket, resulted in an increase of the affinity to gangliosides. Since the configuration of the binding pocket is so decisive for the affinity of the HC to the ganglioside receptor, the proteolytic potency of the associated LC, simultaneously with the affinity of the HC to the ganglioside receptor, either increases or decreases in harmony with the affinity.

In a ligand-receptor-study specific amino acid residues were thus characterised according to the invention in the ganglioside-binding pocket of BoNT/A and substituted in order to increase the affinity to the ganglioside receptor accordingly. The affinity of the mutated H_(C)-fragment was determined in ganglioside and synaptosome-binding assays. Subsequently, the HC exhibiting the same mutations was coupled to LC-A, for which purpose a thrombin-sensitive amino acid sequence was used. The recombinant protein was activated (‘nicked’) by thrombin and resulted in a double-chain molecule, both chains being interlinked by a single disulphide bridge. The activity of the constructs was tested in synaptosomes of rat brain—a preparation releasing transmitters. The extent of transmitter release inhibition was considered as the measure of the degree of activity of the constructs. In addition, the potency of the individual constructs was analysed by means of the isolated nerve-muscle-preparation of the mouse (Hemi-Diaphragma-Assay=HDA), representing the physiological object of clostridial neurotoxins.

Disorders and symptoms which are to be treated with TrapoX are accompanied by a focally increased activity of motor neurons and vegetative nerve cells. The increased activity results in painful cramps of the muscles innerved by these cells and in an excessive liquid secretion from gland cells. Furthermore, facial wrinkles occur in different regions due to the increased activity. The cause is a pathologically increased release of acetyl choline from the peripheral nerve ends. If TrapoX is injected into the affected muscle, a relaxation of the affected muscles, the drying up of secretion and smoothing of the facial skin comes about after a latency of 1-3 days. This is due to an inhibition of the release of acetyl choline by TrapoX. The patient becomes virtually pain-free and the pain provoked by the muscle cramp is alleviated and disappears completely.

The release of acetyl choline is inhibited both in humans as well as in animals. Animal testing is therefore used routinely both as evidence of BoNT in poisoning cases as well as for activity determination of BoNT-drugs (Botox, Dysport, Xeomin). The activity of BoNT is quantified by performing a determination of the LD₅₀ in mice. In this context one determines the dose, killing 50% of the animals of one test group. It is obvious that apart from doses not destroying any animal, doses may be administered killing 100% of the animals from one group. Since the poison is administered systemically (i.p.), a large number of animals thus die painfully of respiratory arrest, caused by a paralysis of the respiratory muscles. In order to avoid animal tests, we have introduced the Mouse Hemi-Diaphragma Assay. With the LD₅₀ test, trial mice die of respiratory paralysis, caused by paralysis of the respiratory muscles. This means that the respiratory muscle, including the innerving nerve (Nervus phrenicus) can be removed from the mouse and be poisoned in vitro. BoNT will bind to its receptors, will enter the cell and be translocated and will finally split its substrate, whereupon the muscle paralyses. There is a strict correlation between the LD₅₀ value and the paralysis of the respiratory muscle. This in vitro test represents, as it were, a watered-down version of the animal test (Wohlfarth K, Goeschel H, Frevert J, Dengler R, Bigalke H, Botolinum A toxis: units versus units. Naunyn Schmiedeberg's Arch Pharmacol. 1997 March; 335(3):335-40).

One can therefore assume that the BoNT, paralysing the diaphragm in vitro, also acts in the living mouse, killing the latter according to the dose administered. This animal test replacement method is so convincing that the Mouse Hemi-Diaphragma-Assay will shortly be accepted for the EU member states by the EU Pharmacopoeia as the official testing method for BoNT. The increased efficacy of TrapoX in the mouse diaphragm preparation thus suggests an increased efficacy in humans as well.

In the more recent past, the BoNT/A complex was used for treating motor dystonias, as well as for attenuating excessive sympathetic activity (see Benecke et al. (1995), Akt Neurol 22, 209ff) and for alleviating pain and migraine (see Sycha et al. (2004), J Neurol 251, 19-30). This complex consists of the neurotoxin, various haemagglutinines and a non-toxic, non-haemagglutinating protein. The complex dissociates rapidly at physiological pH. The resultant neurotoxin is the sole ingredient of the complex which is therapeutically relevant and brings about an alleviation of the symptoms. Since the underlying neurological illness is not cured, the complex needs to be injected again at intervals of three to four months. Depending on the quantity of the injected foreign protein, some patients develop specific BoNT/A-antibodies. These patients become resistant to the neurotoxin. Once antigen-sensitive cells have recognised the neurotoxin and antibodies have been formed, the relevant brain cells are conserved over years. For this reason it is important to treat the patient with preparations of the highest possible activity at the lowest possible dosage. The preparations should furthermore not contain any further proteins of bacterial origin, since these may act as immuno-adjuvants. Such substances attract macrophages, which recognise both the immuno-adjuvants as well as the neurotoxins, presenting them to the lymphocytes, which thereupon respond by forming immunoglobulins. Consequently, only products of extreme purity, not containing any foreign proteins, may be used for therapy.

The present invention now provides a transport protein (Trapo), which is able to overcome the above described problems of the methods known to date.

Preferably, a transport protein (Trapo) is provided, the affinity of which to complex gangliosides is increased at least three fold.

“Binding to nerve cells with a higher affinity than native neurotoxin”. The native neurotoxin is in this case preferably the native neurotoxin of C. botulinum. Preferably, the native neurotoxin is in this context Botulinus neurotoxin A and/or Botulinus neurotoxin B and/or Botulinus neurotoxin G from C. botulinum. The Botulinus neurotoxin prepared in recombinant form from E. coli, which, inter alia, contains the amino acid sequence identical to the native Botulinus neurotoxin, acts in a pharmacologically identical manner to the native Botulinus neurotoxin and is referred to as recombinant Botulinus neurotoxin wild type. The nerve cells mentioned in this case are cholinergic motor neurons. Preferably, the transport protein binds specifically to polysialogangliosides on the nerve cell membrane surface, such as e.g. GD1a, GD1b or GT1b. The binding is determined preferably in vitro. Particularly preferably, the determination is performed by the use of an assay, elucidated in detail in the examples.

The term “modification of the heavy chain of the neurotoxin formed by C. botulinum.” The amino acid and/or nucleic acid sequence of the heavy chain (HC) of the neurotoxin formed by C. botulinum are generally available from publicly accessible databases, for each of the known serotypes A to G (also refer to table 1). Modification includes in this context that at least one amino acid is deleted, added, is inserted into the amino acid sequence, or that at least one amino acid of the native neurotoxin is substituted by another naturally occurring or not naturally occurring amino acid and/or that one amino acid in the stated amino acid sequence is modified post-translationally. Post-translational modifications include in this context glycosylations, acetylations, acylations, de-aminations, phosphorylisations, isoprenylisations, glycosyl phosphatidyl inositolisations and further modifications known to the person skilled in the art.

The HC of the neurotoxin formed by C. botulinum includes three sub-domains, i.e. the amino-terminal 50 kDa-sized translocation domain H_(N), the 25 kDa H_(CN)-domain following thereon, and the carboxyl-terminally situated 25 kDa H_(CC)-domain. Together, the H_(CN)- and H_(CC)-domains are denoted as H_(C)-fragment. The corresponding amino acid sections of the respective sub-domains for the individual serotypes and their variations are apparent from Table 1.

In order to describe in detail hybrid proteins with domains of different BoNT serotypes, the following nomenclature is introduced in what follows. The term scAtAAB denotes e.g. a single-chain neurotoxin (sc), consisting of the four domains LC, H_(N), H_(CN) and H_(CC), each domain, according to its origin, being marked by the capital letter of the respective serotype. This means that scAtAAB is derived from LC, H_(N) and H_(CN), while the H_(CC)-domain of BoNT/A was substituted by BoNT/B. The small letter “t” symbolises an inserted thrombin marker sequence between LC and H_(N).

TABLE 1 Database numbers of the amino acid sequences and distribution of the sub-domains of the seven Botulinus neurotoxins. Database no. of the Number of HC protein the amino H_(C) BoNT sequence acids H_(N) H_(CN) H_(CC) BoNT/A AAA23262 1296 449-866 867-1091 1092-1296 AAM75961 AAQ06331 BTCLAB P10845 1296 449-866 867-1091 1092-1296 CAA36289 1296 449-866 867-1091 1092-1296 CAA51824 1296 449-866 867-1091 1092-1296 I40645 Q45894 BoNT/B AAL11499 1291 442-855 866-1078 1079-1291 AAL11498 CAA73968 1291 442-855 866-1078 1079-1291 AAK97132 1291 442-855 866-1078 1079-1291 A48940 1291 442-855 866-1078 1079-1291 AAA23211 P10844 BAC22064 1291 442-855 866-1078 1079-1291 CAA50482 1291 442-855 866-1078 1079-1291 I40631 BoNT/C1 A49777 1291 450-863 864-1092 1093-1291 BAA14235 BAB71749 CAA51313 S46431 P18640 1291 450-863 864-1092 1093-1291 BAA08418 1280 450-863 864-1083 1084-1280 BAA89713 1280 450-863 864-1083 1084-1280 BoNT/D CAA38175 1276 446-859 860-1079 1080-1276 P19321 S11455 AAB24244 1276 446-859 860-1079 1080-1276 BAA07477 1285 446-859 860-1088 1089-1285 S70582 BAA90661 1285 446-859 860-1088 1089-1285 BoNT/E BAB86845 1252 423-842 843-1066 1067-1252 CAA44558 S21178 CAA43999 1251 423-842 843-1066 1067-1251 Q00496 CAA43998 1251 423-842 843-1066 1067-1251 JH0256 P30995 BoNT/F 1904210A 1274 440-860 861-1086 1087-1274 AAA23263 I40813 P30996 CAA73972 1280 440-861 862-1087 1088-1280 AAA23210 1278 440-861 862-1084 1085-1278 CAA57358 CAA48329 1268 432-853 854-1075 1076-1268 S33411 BoNT/G CAA52275 1297 447-860 861-1086 1087-1297 Q60393 S39791

The present invention relates, in particular, to a transport protein, obtained by modifying the HC of the neurotoxin formed by Clostridium botulinum, the said protein, with a higher affinity than the native neurotoxin, binding specifically to nerve cells and being received by these cells by endocytosis,

The transport protein provided in the present invention exhibits an increased specific affinity of its ganglioside-binding domain to complex polysialogangliosides. The increase of the affinity is preferably attained by substitution or deletion of amino acids.

According to a preferred embodiment the transport protein exhibits an affinity which is at least 15% higher than the native neurotoxin. Preferably, the transport protein exhibits an affinity which is at least 50% higher, particularly preferably at least 80% higher and in particular at least 90% higher than the native neurotoxin.

According to a preferred embodiment the modification of the HC takes place in the region of the H_(C)-fragment of the given neurotoxin. If the modification includes a substitution, deletion, insertion or addition, the latter may also be performed, for example, by specific mutagenesis, methods in this context being known to the person skilled in the art. The amino acids present in the native neurotoxin are in this context modified either by naturally occurring or by not naturally occurring amino acids. Amino acids are, in principle, divided into different physicochemical groups. Aspartate and glutamate belong to the negatively-charged amino acids.

Histidine, arginine and lysine belong to the positively-charged amino acids. Aspargine, glutamine, serine, threonine, cysteine and tyrosine belong to the polar amino acids. Glycine, alanine, valine, leucine, isoleucine, methionine, proline, phenylalanine and tryptophane belong to the non polar amino acids. Aromatic side groups are to be found among the amino acids histidine, phenylalanine, tyrosine and tryptophane. In general, it is preferred to substitute an amino acid by a different amino acid pertaining to another physicochemical group.

According to a preferred embodiment of the invention, the transport protein is a Botulinus neurotoxin serotype A to G.

In a preferred embodiment of the invention, the transport protein is derived from the protein sequence of the clostridium botulinum neurotoxin type A (database no. AAA23262 and CAA51824).

A further embodiment of the present invention relates to a transport protein, wherein at least one amino acid in the positions 1117, 1202 to 1204, 1252 to 1254, 1262 to 1267, 1270 and 1278 to 1279 of the protein sequence of the Clostridium botulinum neurotoxin type A (database no. AAA23262 and CAA51824) has either been removed or been substituted by a naturally occurring or not naturally occurring amino acid.

A further embodiment of the present invention relates to a transport protein, wherein amino acids in positions 1092 to 1296 of the protein sequence of the Clostridium botulinum neurotoxin type A (database no. AAA23262 and CAA51824)—a region including the ganglioside-binding domain—have been substituted by the sequence of

Clostridium botulinum neurotoxin type B protein (database no. AAA23211), amino acids 1079 to 1291,

Clostridium botulinum neurotoxin type C₁ protein (database no. CAA51313), amino acids 1093 to 1291

Clostridium botulinum neurotoxin type D protein (database no. CAA38175), amino acids 1080 to 1276,

Clostridium botulinum neurotoxin type E protein (database no. CAA44558), amino acids 1067 to 1252,

Clostridium butyricum neurotoxin type E protein (database no. CAA43998), amino acids 1067 to 1251,

Clostridium botulinum neurotoxin type F protein (database no. CAA57358), amino acids 1085 to 1278,

Clostridium baratii neurotoxin type F protein (database no. CAA48329), amino acids 1076 to 1268,

Clostridium botulinum neurotoxin type G protein (database no. CAA52275), amino acids 1087 to 1297.

Further H_(CC)-domains suitable for interchangeability with amino acid positions are apparent from Table 1.

A further embodiment of the present invention relates to a composition containing a transport protein according to the invention and at least one intervening molecule (X). The intervening molecule may be a small organic molecule, a peptide or a protein; preferably covalently bonded, e.g. by a peptide-, ester-, ether-, sulphide-, disulphide- or carbon-carbon-bond.

In addition, the intervening molecule includes all known therapeutically active substances. Cytostatics, antibiotics, virustatics, but also immunoglobulins are preferred in this context.

In order to better utilise the increased affinity of the Trapo, it was bound amino-terminally to an LC of BoNT/A, B, C₁, D, E, F or G via an amino acid sequence, which is specifically recognised and split by the protease thrombin, bringing about a specific TrapoX. The active strength of the said TrapoX, in comparison with native BoNT/A, was increased and particularly preferred by a factor of at least 3. This new product, which is free of foreign proteins, will dramatically reduce the stimulation of the immune systems due to the greater purity of the material and the low dosage.

A further embodiment of the present invention relates to a transport protein, wherein the protein is a protease, splitting one or a plurality of proteins of the release apparatus of neurotransmitters, the protease being selected from the group of neurotoxins consisting of the LC of the Clostridium botulinum neurotoxins, in particular of type A, B, C₁, D, E, F and G or a proteolytically active fragment of the LC of a Clostridium botulinum neurotoxin, in particular a neurotoxin of serotype A, B, C₁, D, E, F and G, the fragment exhibiting at least 0.01% of the proteolytic activity of the native protease, preferably at least 5%, particularly preferably at least 50%, in particular at least 90%. Preferably, the transport protein and the protease are derived from the same C. botulinum neurotoxin serotype, in particular and preferably the H_(N)-domain of the transport protein and the protease are derived from the C. botulinum neurotoxin serotype A. The sequences of the proteases are generally accessible at databases and the database numbers are apparent from Table 1. The proteolytic activity of the proteases is determined by way of substrate separation kinetics (see Bina et al. (2002), Biochemistry 41(6), 1717-23).

The LCs are characterised in that they contain the sequence His-Glu-Leu-Xaa-His-(Xaa)₃₃₋₃₅-Glu(Xaa)₈₄₋₉₀-Glu-(Xaa)₁₁-Arg-Xaa-Xaa-Tyr, wherein Xaa may be any amino acid. The transport protein of the present invention is characterised in that the protein and the protease stem from the previous groups of proteins and/or proteases.

According to a further embodiment of the present invention, a method for producing the transport protein is provided. In this case, in a first step a nucleic acid coding for the transport protein is provided. The coding nucleic acid may represent in this context RNA, DNA or mixtures thereof. The nucleic acid may furthermore be modified with regard to its nuclease resistance, such as e.g. by inserting phosphorthioate bonds. The nucleic acid may be produced from a starting nucleic acid, the latter being accessible e.g. by cloning from genomic or cDNA-databases. Moreover, the nucleic acid may be produced directly by solid phase synthesis. Suitable methods are known to the person skilled in the art. If one assumes a starting nucleic acid, a specific modification, e.g. by locality-specific mutagenesis, may be brought about, resulting in at least one addition, insertion, deletion and/or substitution on the amino acid level. The nucleic acid is then linked operatively to a suitable promoter. Suitable promoters for expression in known expression systems are known to the person skilled in the art. The choice of promoter depends in this case on the expression systems used for expression. In general, constitutive promoters are preferred, but inducible promoters may likewise be used. The construct produced in this manner includes at least one part of a vector, in particular regulatory elements, the vector, for example, being selected from X-derivates, adenoviruses, baculoviruses, vaccinia viruses, SV40-viruses and retroviruses. The vector is preferably capable of expressing the nucleic acid in a given host cell.

The invention further provides host cells, which contain the vector and are suitable for expressing the vector. Numerous prokaryotic and eukaryotic expression systems are known in the state of the art, the host cells being selected, for example, from prokaryotic cells such as E. coli or B. megaterium, from eukaryotic cells such as S. cerevisiae and P. pastoris. Although higher eukaryotic cells, such as insect cells or mammal cells, may be used as well, host cells are nevertheless preferred, which, like C. botulinum, do not possess a glycosylation apparatus.

According to a preferred embodiment the nucleic acid codes for the H_(CC)-domain of the C. botulinum neurotoxin. This nucleic acid contains endonuclease-interfaces, flanking the nucleic acid coding for the H_(C)-fragment, the endonuclease sites being compatible with those of other H_(C)-fragments of C. botulinum neurotoxins, in order to permit their easy modular substitution in the gene coding for the transport protein, while the similarity of the amino acid sequence is preserved.

If a composition according to the invention is provided, which, apart from the transport system, further contains at least one intervening molecule, and this intervening molecule, a peptide or protein, is functionalised either with a carboxy-terminal cysteine or a mercapto-group, then, in an analogous manner, as described before, the peptide and/or protein may be produced recombinantly, for example by using binary vectors or various host cells. If the same host cell is used for the expression both of the transport protein and the peptide or protein, an intermolecular disulphide bond is preferably formed in situ. For a more efficient production in the same host cell, the nucleic acid coding for the peptide or protein may also be translated with that of the transport protein in the same reading frame, so that a single-chain polypeptide is produced. In this case preferably an intramolecular disulphide bond is formed in situ. For simple hydrolysis of the likewise present peptide cross-linking between the transport protein and the peptide and/or protein, an amino acid sequence is inserted at the amino-terminus of the transport protein, which is either specifically recognised and separated by the protease thrombin or by a specific endoprotease of the host cell.

If this is not possible, an appropriate intermolecular disulphide-linkage, after separate purification of the transport protein and the protein, may subsequently be brought about by oxidation processes known to the person skilled in the art. The peptide or protein may also be obtained directly by synthesis or fragment condensation. Appropriate methods are known to the person skilled in the art.

The transport protein and the peptide, or protein respectively, are subsequently purified. For this purpose methods are used, known to the person skilled in the art, such as e.g. chromatography-methods or electrophoresis.

A further embodiment of the present invention relates to the pharmaceutical composition, including the transport protein and optionally a pharmaceutically acceptable excipient, a diluent and/or an additive and which is suitable to treat the following disorders or diseases: hemi-facial spasms, spasmodic torticollis, spasticities, dystonias, migraine, pain, disorders of the neck and lumbar vertebral column, strabism, hypersalivation and depressive diseases.

The pharmaceutical composition is suitable for oral, intravenous, subcutaneous, intramuscular and topical administration. Intramuscular administration is preferred. A dosing unit of the pharmaceutical composition contains approximately 0.1 pg to 1 mg of transport protein and/or the composition according to the invention.

A further embodiment of the present invention includes a cosmetic composition, consisting of the transport protein and a pharmaceutical excipient, a diluent and/or an additive, suitable for treating hyperhydrosis and very pronounced facial wrinkles. The cosmetic composition is suitable for oral, intravenous, subcutaneous, intramuscular and topical administration. Intramuscular administration is preferred. A dosing unit of the cosmetic composition contains about 0.1 pg to 1 mg of transport protein and/or the composition according to the invention. The cosmetic composition is suitable to treat hyperhydrosis and facial wrinkles.

The transport protein described in the present invention may be produced by a suitable host cell, such as e.g. Escherichia coli, Saccharomyces cerevisiae, Pichia pastoris or Bacillus megaterium, which multiplies a recombinant expression vector, the vector coding for a transport protein.

The present invention is elucidated by the accompanying drawings, wherein:

FIG. 1 shows that the affinity of the mutated H_(C)-fragment of BoNT/A to synaptosome membrane preparations from the rat brain is three times higher than that of the H_(C)-fragment of the wild type of BoNT/A.

FIG. 2 shows the binding of different BoNT/A H_(C)-fragment mutants to rat brain synaptosomes, the affinity of the BoNT/A H_(C)-fragment wild type being set to 100% as a standard. The first column shows the affinities of the BoNT/A mutants, showing mutations of the amino acids Y1117 resulting in an increase. The second column shows further BoNT/A-mutants. The third column shows the affinities of BoNT/A-mutants exhibiting double mutations, which enhance the binding to nerve cell membranes (synaptosomes).

FIG. 3 shows the increased neurotoxicity of the Y1117A-mutant of BoNT/A in comparison with the BoNT/A-wild type on the isolated nervus phrenicus diaphragm muscle-preparation of the mouse.

FIG. 4 shows the binding of the four BoNT/A H_(C)-fragment hybrids H_(C)AB, H_(C)AC, H_(C)AE and H_(C)AT (T=tetanus neurotoxin) in nerve cell membranes (synaptosomes), the BoNT/A H_(C)-fragment wild type being set to 100% as a standard.

FIG. 5 shows the increased neurotoxicity of the total toxin hybrids consisting of BoNT/A and either the H_(C)-fragment or the H_(CC)-domain of BoNT/B in comparison with the BoNT/A-wild type in the isolated nervus phrenicus—diaphragm muscle-preparation of the mouse.

In detail, the present invention contains a transport protein (Trapo), formed by a modification of the HC of the neurotoxin produced by Clostridium botulinum, preferably specifically binding to neurons, accommodated intracellularly by receptor-mediated endocytosis and translocated from the acid endosomal compartment into the cytosol of neurons. This protein is used as a transporting means in order to introduce into the cells proteases and other substances bound to the said transporting means, unable to penetrate physiologically into the plasma membrane and to reach the cytosol of nerve cells. The substrates of the proteases are intracellularly localised proteins and peptides participating in the transmitter release. After separation of the substrates, the specific functions of the neurons are blocked; the cells themselves are not damaged. One of these functions is exocytosis, bringing about the neurotransmitter release. If the release of transmitters is inhibited, the transmission of signals from cell to cell is blocked. For example, striated muscles are paralysed if the release of acetyl choline is inhibited at the neuromuscular contact point. This effect may be used therapeutically, if TrapoX is applied to nerve ends of spastic or dystonic muscles. Other active substances are, for example, substances exhibiting anti-viral action. Conjugated with Trapo, they might be of use for treating viral infections of the nervous system. The present invention also relates to the use of a transport protein for inhibiting the release of neurotransmitters.

If patients are treated with the native forms of BoNT/A and B, injection of these non-human proteins, despite the low dosage, causes the formation of antibodies, so that the therapy must be stopped in order to prevent anaphylactic shock. By applying a substance with the same active mechanism having a higher transport efficiency of the enzymatic activity, the dosage may be lowered drastically and the formation of antibodies will not occur. These properties are attributed to the transport protein described herein.

Although examples are stated for application, the suitable mode of application and the dosage is, in general, individually determined by the treating physician. Such decisions are routinely made by each physician well versed in the relevant special field. Thus, the mode of application and the dosage of the neurotoxin may e.g. be selected in accordance with the invention described herein, based on criteria such as the solubility of the selected neurotoxin or the intensity of the pain to be treated.

The treatment interval for native BoNT/A and B is currently three to four months on average. Prolonging this interval would reduce the risk of the formation of antibodies and allow a longer treatment period with BoNT. The increase of LC in the cytosol would extend its decomposition timewise and would thus also prolong the duration of action. The transport protein described here exhibits a higher affinity and reception rate than the native HC-A.

The following example merely serves for elucidation and should not be contemplated in a limiting manner.

EXAMPLES

Recombinant Expression of the Genetically Engineered TrapoX in E. coli

The DNA-sequence of the HC of BoNT/A was amplified in chromosomal DNA of Clostridium botulinum (database no. AAA23262) by means of PCR. For this purpose, by means of specific oligonucleotides, the codon for the amino acid tyrosine 1117 was substituted by a base triplet coding for the amino acid residue of alanine. Furthermore, the 5′-end of the gene was supplemented by a DNA-sequence, coding for the amino acids of the recognition sequence of thrombin. This DNA-sequence was inserted into a bacterial expression vector. The inserted gene for Trapo was in this case fused with an oligonucleotide at the 3′-end, coding for a carboxy-terminal affinity peptide such as e.g. the Strep-day, 6xHN-day or His₆-day. The expression vector pAR-Trapo produced in this manner is the starting basis for adding carrier molecules, such as the LC of the BoNT.

The DNA-sequence of the LC of BoNT/A was amplified by the PCR-method in the chromosomal DNA-sequence of Clostridium botulinum (database no. AAA23262) and inserted into the expression vector pAR-Trapo upstream of the coded thrombin recognition sequence. The expression vector pAR-TrapoX thus produced was transformed into an E. coli K12 strain and the expression of the protein TrapoX was induced under the conditions of Biological Safety Level 2 and in compliance with the rules and regulations issued for the project by the district government of Hanover, file reference 501g.40654/3/5713. The over-expressed TrapoX was isolated in an affinity-chromatographic manner, following the directions of the manufacturer, as a single-chain protein with a molecular weight of 150 kDa. The protein was subsequently hydrolysed with thrombin conjugated on sepharose, bringing about a pure protein, the two chains of which remained interlinked by a disulphide-bridge.

Compared with the wild type of BoNT/A, this protein exhibited an affinity, increased by 300%, to isolated ganglioside GT1b immobilised on micro titre plates and to synaptosome membrane preparations from rat brain (FIG. 1). The catalytic activity of the LC-A was not changed, as has been shown in the in vitro splitting of recombinant SNAP-25. The potency of the TrapoX with regard to inhibition of the neurotransmitter release in functional synaptosomes from rat brain had increased by 300%, compared with the native BoNT/A recovered from Clostridium botulinum. In nerve muscle-preparations of the mouse (HDA), the potency of the TrapoX was likewise increased by 300% compared with the native BoNT/A (FIG. 2).

Measurement of the Binding to Rat Brain Synaptosomes and the Neurotoxicity in the HDA of Different BoNT/A-Mutants

The binding of radioactively marked H_(C)-fragments to rat synaptosomes was measured as stated in Rummel et al., J. Mol. Biol. 326 (2003), 835-847. The neurotoxicity of the BoNT/A-mutants was determined as described by Habermann et al., Naunyn Schmiedeberg's Arch. Pharmacol. 311 (1980), 33-40.

The comparison of the binding of different BoNT/A-mutants as compared with the wild type is shown in the following table:

Table relating to FIG. 2 Mutation % vs. wild type Standard deviation Wild type 100.0 15.00 Y1117A 332.3 29.00 Y1117C 324.2 44.75 Y1117D 124.4 26.94 Y1117E 183.3 27.95 Y1117F 235.9 38.41 Y1117G 112.8 21.34 Y1117H 120.0 22.29 Y1117I 248.1 21.95 Y1117L 253.6 25.65 Y1117M 182.8 18.41 Y1117N 250.3 20.13 Y1117P 150.3 14.98 Y1117Q 187.3 28.19 Y1117R 115.4 16.80 Y1117S 199.2 32.65 Y1117T 264.1 28.55 Y1117V 346.9 37.61 F1252Y 208.0 38.36 H1253K 153.0 9.24 V1262I 97.8 9.38 Q1270N 122.3 37.81 L1278H 170.0 61.59 G1279N 153.6 44.54 Y1117C/H/1253K 324.8 22.72 Y1117V/H1253K 332.9 33.48

The mutation of individual determined amino acids within the ganglioside binding pocket of BoNT/A resulted in an increase of the binding to nerve cells. Preferably, in position 1117, tyrosine is substituted by alanine, cysteine or valine. In particular, the substitution of the tyrosine residue in position 1117 by alanine results in an increase of the affinity to about 330%.

Further mutations of individual amino acids from the ganglioside binding pocket in position 1252 and 1253 result likewise in an increase of the binding. In particular, the mutation of F1252 in tyrosine and H1253 in lysine resulted in an increase of the affinity by 110%, and 50% respectively.

Furthermore, increases of the binding to nerve cells can be expected in mutations in positions 1202, 1262, 1270, 1278 and 1279.

Moreover, mutants of BoNT/A were also tested with double mutations, in which case, in particular, the mutants Y1117C/H1253K and Y1117V/H1253K resulted in an increase of the binding to synaptosomes (cf. FIG. 2).

It was furthermore determined that the increase of the binding, particularly of the mutant Y1117A of BoNT/A resulted in an increase of the neurotoxicity in the N. phrenicus—neurotoxicity assay (HDA-Assay) (FIG. 3).

Determination of Binding and Neurotoxicity of BoNT/A H_(CC)-Hybrids

The determination of the binding and the neurotoxicity was performed as described above.

The results are reflected in the following table and further in FIGS. 4 and 5.

Table relating to FIG. 4 Mutation % vs. wild type standard deviation HcA wt 100.0 10.4 HcAB 249.2 19.1 HcAC 393.4 57.9 HcAE 22.0 5.3 HcAT 210.2 22.5

Substitution of the H_(CC)-domain of BoNT/A by the other serotypes, in particular C. botulinum neurotoxin B and C. botulinum neurotoxin C, resulted in an increase of the binding to nerve cells. It was furthermore observed that the substitution of the H_(CC)-domain of H_(C)-fragment of BoNT/A by the corresponding domain of tetanus neurotoxin likewise resulted in an increase of the affinity in nerve cells. The affinity changes also apply to the substitution of the H_(CC)-domain in the entire BoNT/A. FIG. 5 shows in this context that in a hybrid scAtAAB the increase of affinity has a similar effect on increased neurotoxicity. If, instead of the H_(CC)-domain, the entire H_(C)-fragment scAtAAB is substituted, corresponding results are observed. In particular, it was observed that an improvement of the neurotoxicity by about 350% was noted when substituting the H_(CC)-domain or the H_(C)-fragment of BoNT/A by that of BoNT/B.

Determination of Binding of the BoNT-Mutants to the Ganglioside GT1b

Ganglioside GT1b [NAcNeuα3Galβ3NAcGal β4(NAcNeuα8NAcNeuα3)Galβ4Glcβ] (Sigma-Aldrich) is dissolved in methanol and applied to high-affinity 96-cup polystyrene-micro titre plates (Corning; 1 μg GT1b in 100 μl/cup) or, in the case of competition assays to high-affinity CS single fracture strip plates with ¹²⁵I-BoNTs (Greiner Bio-ohne; 0.1 pg GT1b in 100 μl/cup). The solvent is evaporated at room temperature and the cups are rinsed three times with a binding buffer (10 mM Tris-HCl, 10 mM Na₂HPO₄, 0.5% BSA, pH7.2). The non specific binding sites are then blocked by incubation for two hours in PBS/Tween [140 mM NaCl, 7 mM KCl, 10 mM Na₂HPO₄, 1.8 mM KH₂PO₄, 0.05% (VN) Tween 20, pH 7.2], supplemented by 3% (w/v) BSA. The binding assays are carried out in binding buffers (100 μl/cup) for 2 hours at room temperature either with increasing quantities of the wild type or specific quantities of the mutants. Unbound protein is removed in 3 rinsing steps, each with 250 μl PBS/Tween buffer. Bound H_(C)-fragments are identified by incubation with Strep Tactin conjugated with alkaline phosphatase (ST-AP, IBA GmbH) in a binding buffer for a duration of 2 hours at room temperature according to manufacturer's instructions. p-nitrophenyl phosphate (1 mg/ml in 100 mM glycine, 1 mM MgCl₂, 1 mM ZnCl₂, pH 10.4), which ultimately serves as substrate for the alkaline phosphatase. The desphorphorylation reaction is stopped by adding a 3 M NaOH solution and the extinction is measured at 405 nm using a Spectra Count micro plate reading device (Packard). The competition assays are performed over a period of 2 hours at room temperature in a 100 μl binding buffer with 700000cpm/cup [1251]-BoNT, different quantities of native BoNT or recombinant H_(C)-fragment. After incubation and removal of the supernatants the cups are rinsed three times with PBS/Tween buffer, dried and separated. The quantities of bound radioactively marked BoNT are then determined in an automatic γ-counter (Wallac 1480 Wizard 3). 

1. A transport protein, obtainable by modification of the heavy chain of Clostridium botulinum type A (BoNT/A), wherein the complete Hc-fragment of the BoNT/A heavy chain is substituted by the complete Hc-fragment of a different Clostridium neurotoxin type or wherein the complete Hcc-fragment of the BoNT/A heavy chain is substituted by the complete Hcc-fragment of a different Clostridium neurotoxin type.
 2. The transport protein according to claim 1, wherein the protein binds specifically to nerve cells and enters the cells by endocytosis.
 3. The transport protein according to claim 1, wherein the protein binds specifically to complex gangliosides of cholinergic motor neurons, localised in the plasma membrane, preferably GT1b.
 4. The transport protein according to claim 3, wherein the ganglioside-binding domain of the transport protein includes substitutions and deletions of amino acids, influencing the increased affinity.
 5. The transport protein according to claim 1, wherein the protein exhibits an affinity at least 15% higher than the native neurotoxin.
 6. The transport protein according to claim 1, wherein said transport protein binds to nerve cells with a higher affinity than native Clostridium botulinum type A.
 7. The transport protein according to claim 1, wherein the amino acids 867-1296 of BoNT/A are substituted by the following sequences: amino acids 866-1291 of BoNT/B; amino acids 864-1291 or 864-1280 of BoNT/C1; amino acids 860-1276 or 860-1285 of BONT/D; amino acids 843-1252 or 843-1251 of BoNT/E; amino acids 861-1274 or 862-1280 or 862-1278 or 854-1268 of BoNT/F; or amino acids 861-1297 of BoNT/G. 8-13. (canceled)
 14. The transport protein according to claim 1, wherein the amino acids 1092 to 1296 of the Clostridium botulinum neurotoxin type A, containing the ganglioside-binding domain, are substituted by the following sequences: Clostridium botulinum neurotoxin type B protein, amino acids 1079 to 1291, Clostridium botulinum neurotoxin type C₁ protein, amino acids 1093 to 1291, or 1084 to 1280, Clostridium botulinum neurotoxin type D protein, amino acids 1080 to 1276, or 1089 to 1285, Clostridium botulinum neurotoxin type E protein, amino acids 1067 to 1252, or 1067 to 1251, Clostridium botulinum neurotoxin type F protein, amino acids 1087 to 1274, 1088 to 1280, 1085 to 1278, or 1076 to 1268, Clostridium botulinum neurotoxin type G protein, amino acids 1087 to
 1297. 15-39. (canceled)
 40. The transport protein according to claim 1, wherein said different Clostridium neurotoxin type is BoNT/B, BoNT/C1 or Clostridium tetani.
 41. A composition comprising the transport protein according to claim 1, wherein said transport protein is coupled to a clostridial neurotoxin protease.
 42. A method for treating a disorder or disease for which a therapy with botulinum neurotoxin is indicated, said method comprising administration of an effective amount of the composition according to claim
 41. 43. The method of claim 42, wherein the disorder or disease is one of the following: hemi-facial spasm, spasmodic torticollis, spasticities, dystonias, migraine, pain, disorders of the neck and lumbar vertebral column, strabism, hypersalivation and depressive diseases.
 44. A method for treating a cosmetic indication selected from hyperhidrosis and pronounced facial wrinkles, said method comprising administration of an effective amount of the composition according to claim
 41. 